1. Field of the Invention
The present invention relates to an automatic changeover system, an automatic changeover station and an automatic changeover method. More particularly, the present invention relates to an automatic changeover system for communication networks which changes over from one communication network (such as a wireless LAN) to another (such as cellular telephone network and Personal Handyphone System network), an automatic changeover station for the same and an automatic changeover method of communication networks.
2. Description of the Related Art
The wireless terminal (station) is known, in which two kinds of communication methods can be operated.
The two kinds of communication methods are exemplified in a communication method of a LAN (Local Area Network) and a communication method of a mobile telephone network such as cellular telephone network and a PHS (Personal Handyphone System) network.
When a user carries out a communication (including calling and incoming) by using the station based on the communication method of a LAN, the station accesses to a wireless LAN access point and then communicates with another station (a wireless LAN communication) through a first wireless communication network which is used for the wireless LAN
When a user carries out a communication (including calling and incoming) by using the station based on the communication method of a PHS network, the station accesses to a cell station and then communicates with another station (a PHS communication) through a second wireless communication network which is used for the PHS network.
For example, when a user carries out the wireless LAN communication by using the station, the communication (line) is cut or the communication quality decreases according to the decrease of electric field intensity of electromagnetic wave in case that the station goes out of the service area in which the station can performs the wireless LAN communication.
For this reason, when the user uses the station, the user has to be conscious of the condition of the electromagnetic wave. Also, the user has to change over from the wireless LAN communication (the first wireless communication network) to the PHS communication (the second wireless communication network) by himself/herself if necessary. Therefore, the technique is desired that enables user to carry out the communication without being conscious of the condition of the electromagnetic wave.
The communication charge for the first wireless communication network (the communication charge for the wireless LAN communication) is more inexpensive than that for the second wireless communication network (that for the PHS communication). The technique is desired that the lower-cost communication method has a priority for performing the communication over other communication methods.
In conjunction with the above description, Japanese Laid Open Patent Application (JP-A-Heisei 9-23555) discloses the following a common use telephone device.
The common use telephone device includes the transmitting/receiving device which copes with a plurality of communication networks. The device includes a transmitting/receiving sections, a telephone call quality watch section, a changeover section, the other party telephone number memory section, a repeated call section and a man-machine interface section. The transmitting/receiving sections transmit/receive signals in the communication network in which the signals can be communicated. The telephone call quality watch section diagnoses the degradation of the telephone call quality based on the signals received in the transmitting/receiving section. The changeover section selects any of the transmitting/receiving sections based on the output from the telephone call quality watch section. The other party telephone number memory section stores the telephone number of other party of the communication. The repeated call section has a function which performs the repeated call to the telephone number which is stored in the other party telephone number memory section based on the output of the telephone call quality watch section and the operation of the changeover section. The man-machine interface section controls the interface for the user.
Japanese Laid Open Patent Application (JP-A 2001-128240) discloses the following a communication method of the multiple mobile terminal and that communication system.
The communication method of the multiple mobile terminal includes: carrying out a communication between a mobile terminal and another terminal in a first wireless communication network; detecting a degradation of a condition of a electromagnetic wave received by the mobile terminal; and changing over the communication between the mobile terminal and the other terminal from the first communication network to the second communication network.
Japanese Laid Open Patent Application (JP-A 2000-209644) discloses the following a multiple terminal device for a wireless communication.
The multiple terminal device for a wireless communication includes a transmitting section, a receiving section, a controlling section and a traffic data recognizing section. The transmitting section and the receiving section can perform a communication in a plurality of wireless communication networks, based on a corresponding one of a plurality of communication methods, which are different, each other. The controlling section connects a communication line of the wireless communication network selected from the plurality of the wireless communication networks through the transmitting section and the receiving section. The traffic data recognizing section recognizes a traffic data of the communication line of the wireless communication network based on a received signal received from the receiving section. Then, the controlling section selects a wireless communication network, of which a communication line is not used so much, from the plurality of the wireless communication networks based on the traffic data obtained from the traffic data recognizing section, when connecting to the communication line.
Japanese Laid Open Patent Application (JP-A 2000-278756) discloses the following a wireless communication device.
The wireless communication device includes a plurality of wireless communication means, a judging means and a connection changeover means. The plurality of wireless communication means can perform a communication by connecting to each of a plurality of wireless communication networks of which wireless communication methods are different each other. The judging means judges whether a certain condition is satisfied when one of the plurality of the wireless communication means is carrying out the communication to another party by connecting to one of the plurality of wireless communication networks, and another one of the plurality of the wireless communication means is standing by for the communication. The connection changeover means makes the one of the plurality of wireless communication means end the communication and then make the other one of the plurality of wireless communication means start the communication to the other party by connecting to another of the plurality of wireless communication networks when the judging means judges that the certain condition is satisfied.
Japanese Laid Open Patent Application (JP-A 2001-54168) discloses the following a communication method changeover wireless terminal and a communication method changeover method.
The communication method changeover wireless terminal can perform a wireless communication between a plurality of base stations of a plurality of a mobile communication systems of which kinds are different each other by changing over software. The communication method changeover wireless terminal includes a multimode transmitting-receiving means, a programmable device, a quality signal receiving means, a quality signal sending means, a module addition control means and a module release control means. The multimode transmitting-receiving means includes an antenna and a feeder cable which correspond to sending and receiving wireless signals among the plurality of base stations of the plurality of the mobile communication systems of which communication methods and frequencies are different each other. The programmable device can connect to the multimode transmitting-receiving means, and code programs regarding the various functions necessary for the communication such as the demodulation, the demodulation and filter. The quality signal receiving means controls the programmable device to receive wireless signals from the plurality of base stations of the plurality of the mobile communication systems at the substantial same time. The quality signal sending means calculating a communication quality of system (QoS) of each mobile communication system based on property data of propagation circumstances, which is detected in accordance with the signals received from each base station by control of the quality signal receiving means, module addition control means, and system specific property data of each mobile communication system. Then, the quality signal sending means sends the communication quality of system (QoS) of each mobile communication system to the base station which is in communication. The module addition control means adds the control of a software module, which realizes the communication function for another mobile communication system, to the control of the programmable device, when changing over from the mobile communication system to the other mobile communication system. The module release control means releases the software module, which realizes the control of the unnecessary mobile communication function, from the control of the programmable device.
Japanese Laid Open Patent Application (JP-A-Heisei 9-163450) discloses the following a mobile communication multiple terminal.
The mobile communication multiple terminal has transmitting-receiving functions of two different mobile communication systems. The mobile communication multiple terminal includes the means which automatically or manually changes over the mobile communication systems for awaiting the signal.